Simplify union and prologue handling, and escape union and lex/parse

params with digraphs.
* data/bison.m4 (b4_pre_prologue, b4_post_prologue): Set their default
values to the empty string since these are no longer guaranteed
initialized by the front-end.
* data/glr.c, data/glr.cc, data/lalr1.cc, data/push.c, data/yacc.c: Add
braces around b4_user_stype since this is no longer done by the
front-end.
* src/files.c, src/files.h (pre_prologue_obstack,
post_prologue_obstack): Remove.
* src/muscle_tab.c (muscle_pair_list_grow): Don't duplicate header
comments here.  Use MUSCLE_OBSTACK_SGROW so that values are escaped
with digraphs.  This fixes lex params and parse params.
* src/muscle_tab.h (muscle_pair_list_grow): Update comments.
* src/output.c (prepare): Remove muscle insertion of the prologues.
(output): Remove freeing of pre_prologue_obstack and
post_prologue_obstack.
* src/parse-gram.y (prologue_declaration): Use muscle_code_grow rather
than prologue_augment for prologue parsing so you don't need prologue
obstacks.
(grammar_declaration): Use `braceless' instead of "{...}" so that
braces are already stripped and code is escaped with digraphs.
* src/reader.c (prologue_augment): Remove.
(reader): Remove initialization of pre_prologue_obstack and
post_prologue_obstack.
* src/reader.h (prologue_augment): Remove.

* data/c.m4: Remove stray parenthesis.

src/parse-gram.h

@@ -100,72 +100,14 @@
      PERCENT_UNION = 313
    };
 #endif
-/* Tokens.  */
-#define GRAM_EOF 0
-#define STRING 258
-#define INT 259
-#define PERCENT_TOKEN 260
-#define PERCENT_NTERM 261
-#define PERCENT_TYPE 262
-#define PERCENT_DESTRUCTOR 263
-#define PERCENT_PRINTER 264
-#define PERCENT_LEFT 265
-#define PERCENT_RIGHT 266
-#define PERCENT_NONASSOC 267
-#define PERCENT_PREC 268
-#define PERCENT_DPREC 269
-#define PERCENT_MERGE 270
-#define PERCENT_CODE 271
-#define PERCENT_DEBUG 272
-#define PERCENT_DEFAULT_PREC 273
-#define PERCENT_DEFINE 274
-#define PERCENT_DEFINES 275
-#define PERCENT_ERROR_VERBOSE 276
-#define PERCENT_EXPECT 277
-#define PERCENT_EXPECT_RR 278
-#define PERCENT_FILE_PREFIX 279
-#define PERCENT_GLR_PARSER 280
-#define PERCENT_INITIAL_ACTION 281
-#define PERCENT_LANGUAGE 282
-#define PERCENT_LEX_PARAM 283
-#define PERCENT_LOCATIONS 284
-#define PERCENT_NAME_PREFIX 285
-#define PERCENT_NO_DEFAULT_PREC 286
-#define PERCENT_NO_LINES 287
-#define PERCENT_NONDETERMINISTIC_PARSER 288
-#define PERCENT_OUTPUT 289
-#define PERCENT_PARSE_PARAM 290
-#define PERCENT_PURE_PARSER 291
-#define PERCENT_PUSH_PARSER 292
-#define PERCENT_PUSH_PULL_PARSER 293
-#define PERCENT_REQUIRE 294
-#define PERCENT_SKELETON 295
-#define PERCENT_START 296
-#define PERCENT_TOKEN_TABLE 297
-#define PERCENT_VERBOSE 298
-#define PERCENT_YACC 299
-#define BRACED_CODE 300
-#define CHAR 301
-#define EPILOGUE 302
-#define EQUAL 303
-#define ID 304
-#define ID_COLON 305
-#define PERCENT_PERCENT 306
-#define PIPE 307
-#define PROLOGUE 308
-#define SEMICOLON 309
-#define TYPE 310
-#define TYPE_TAG_ANY 311
-#define TYPE_TAG_NONE 312
-#define PERCENT_UNION 313
-
 
 
 
 #if ! defined YYSTYPE && ! defined YYSTYPE_IS_DECLARED
 typedef union YYSTYPE
 {
-/* Line 1535 of yacc.c  */
+
+/* Line 1537 of yacc.c  */
 #line 97 "parse-gram.y"
 
   symbol *symbol;
@@ -176,11 +118,12 @@ typedef union YYSTYPE
   assoc assoc;
   uniqstr uniqstr;
   unsigned char character;
-}
 
-/* Line 1535 of yacc.c  */
-#line 183 "parse-gram.h"
-	YYSTYPE;
+
+
+/* Line 1537 of yacc.c  */
+#line 126 "parse-gram.h"
+} YYSTYPE;
 # define YYSTYPE_IS_TRIVIAL 1
 # define yystype YYSTYPE /* obsolescent; will be withdrawn */
 # define YYSTYPE_IS_DECLARED 1